Cell phones represent the best and worst of modern wireless
technology. Cell phones are one of the most popular tools of the
early twenty-first century, facilitating business, recreation, and
vital emergency communication. As the technology has become more
popular, the social and safety problems associated with its wide-spread
use have become more apparent. Cell phones are valuable tools, but
they are also a significant distraction; The consequences of this
distraction can range from socially inappropriate to life-threatening
depending on the circumstances.

We have all experienced the down-side of cell phone use; Cell phones
ring in movie theaters, meetings, restaurants, and while we are in
important face-to-face conversations. In some parts of the world
restaurant and theater owners have gone so far as to employ cell phone
jamming technology to limit the disruption caused by inappropriate
cell-phone use. Cell phones are implicated in significant and
increasing numbers automobile crashes each year, resulting in a
national trend toward legislating restrictions on cell phone use while
driving.

Partly this is a social problem; some people should learn to be more
considerate in the use of this technology. But part of the problem is
technological; A cell phone is deaf and blind, and depends completely
on the user to manage its state. Providing users better tools to
manage the state of their phones, tools which require less of their
attention and can do more automatically, can only help. We can't stop
inconsiderate people from using the technology in an inconsiderate
way, but we can help responsible people make better and safer use of
cell phones.

If it were possible to build a phone that could determine the user's
circumstances or context, this information could be used to
change the phone's behavior in useful ways. Such a context
aware phone could automatically switch profiles when the user
enters a restaurant, sits in the driver's seat of a car, etc.
In the case of phone management, nearly all of the complexity lies in
the sensing and determination of context. Once the context is known,
very simple rules can produce behavior that appears quite intelligent.

Context awareness requires sensing and inference to determine the
user's context. Both the sensors and the inference techniques must be
chosen carefully in order to make the best possible use of the limited
real estate and computing power available in a portable form factor.

We have chosen an array of sensors for the first context-aware cell
phone prototype that allow us to determine important aspects of the
user's state. All of these sensors are comparatively low-bandwidth
except for the microphone, which we will band-limit to regions of
interest for human speech. Managing bandwidth is important, because
there is a direct correspondence between bandwidth, signal processing,
and power consumption.

Precision three-axis accelerometer.
The precision three-axis accelerometer provides information about the user's activity state (walking, standing still, etc.) and may additionally be used for gestural input.

IR tag reader and IR active tags. The combination of IR
active tags and tag reader will be used to identifying important
indoor locations (meeting room, office, etc) and to recognize special circumstances, such as sitting in the driver's seat of a car.

Microphone.
The microphone will be used to recognize the user's voice and determine whether the user is in a conversation.

The key to building a successful context-aware cell phone (or any
other context aware application) is an effective context sensing and
modeling system. The architecture of this system is quite important,
since it must be powerful enough to do its job but simple enough to be
implemented under tight resource constraints.

The result of our research into building a system with the required
power and flexibility is the MIThril
Inference Engine. The MIThril Inference Engine (MIE) provides a
simple, flexible, and modular foundation for constructing
context-aware applications. We are currently implementing the the MIE
on our Linux-based MIThril computing
cores, with the eventual goal of porting its core features to the
Motorola
i85s iDen phone.

The context-aware cell phone project began in late summer 2001 with
the donation of a Motorola
i85s iDen phone and service by Motorola.

Since that time we have been focusing on sensor design, data
acquisition, and the design of the MIThril Inference Engine that will
enable us to implement the cell-phone management application. We have
done preliminary work with the i85s hardware and Java interpreter, and
verified that we are able to program the phone and talk to it over the
serial port.

The first phase of the implementation will interface the i85s with the
clothing-integrated MIThril wearable. The phone-management software
will run as a MIE application on the Linux-based MIThril computing
cores, and will communicate with a light-weight Java application on
the i85s to change the phone's profile. This configuration will allow
us to prototype the phone-management application with fewer bandwidth
and computing constraints.

The second phase will integrate the i85s, sensors, and additional
signal processing in a single package, resulting in a self-contained
application.

We are working on the phase one implementation right now, and have a
preliminary implementation of the motion, GPS, and tag-reader
components working. Open problems include the Java interface for
switching the phone profile and a light-weight speaker-identification
model.